This invention relates generally to key operated protective devices and especially to power control devices which can be employed to prevent the unauthorized use of machinery. More particularly, the present invention relates to key operable safety switches of the type used as safety guard switches.
While not limited thereto in its utility, the present invention is particularly well suited for use as a safety guard switch for electrically powered machinery. Such switches are known in the art as exemplified by the disclosure of European Patent Specification 175,156. A switch of the type shown in this European Patent Specification generally includes an actuating member or key, a housing, a contact, a switching roller and roller parts. In operation of the prior art safety switch, the key is inserted through an opening in the housing, axially displacing the roller parts and releasing the switching roller. Subsequent rotation of the key rotates the switching roller thereby causing the switch contacts to either close or open.